The subject matter in this application is related to that in U.S. Pat. No. 5,447,150. That patent is incorporated by reference.
1. Field of the Invention
This invention relates to a dispensing device, and more specifically, to a device suitable for dispensing discrete amounts of fluid.
In particular, the invention is concerned with a dispensing device of the type where the metered dose is administered in response to the inhalation of the patient.
2. Background of the Disclosure
Metered dose inhalers are well known in medicine for treatment, or alleviation of the effects of respiratory complaints, for example asthma. Breath-actuated devices are also known, and have been the subject of many patent applications.
GB 1288971; GB 1297993; GB 1335378; GB 1383761; GB 1392192; GB 1413285; WO85/01880; GB 2204799; U.S. Pat. No. 4,803,978 and EP 0186280A describe inhalation-actuated dispensing devices for use with a pressurised aerosol dispensing container. The device includes a dispensing container and the container includes a valve capable of releasing a metered amount of the aerosol contents, when an internal spring operating the valve is compressed by a sufficient amount. The dispensing device often comprises a chamber having a mouthpiece, air inlets, actuating means for causing the actuation of the valve in the dispensing container, a latching means for releasably retaining said metering valve in a charged position, and an inhalation responsive means for releasing the latch, such that a metered amount of aerosol compound is discharged into the region of the mouthpiece. The overall objective is to give co-ordination of discharge of medicament from the aerosol container with inhalation of the patient, thus allowing a maximum dose of medicament to reach the bronchial passages of the lungs.
The latching means is often connected to a valve which moves from a latching position to a dispensing position in response to a partial vacuum developed upon inhalation.
EP-A-0045419 describes an inhalation device having biassing means which are alone of insufficient force to depress the container but which together are of sufficient force to do so.
EP-A-186280 describes a device which employs magnets to control the release of the aerosol container.
U.S. Pat. No. 3,605,738 describes devices in which the aerosol container communicates with the mouthpiece via a metering chamber. A metered quantity of the aerosol compound is discharged into the metering chamber and this is conveyed to the mouthpiece via an inhalation-actuated valve.
GB 1269554 describes a device wherein the aerosol container is moveable by a lever and cam system into a charged position held by a latch, a pressure differential acting to trip the latch and move the valve of the container to a discharge position.
U.S. Pat. No. 5,447,150, incorporated by reference herein, disclosed a metered dose inhaler, wherein the release of the medicament is actuated by the inhalation of the patient. That patent disclosed an inhalation-actuated device which is more simple and compact than the then-prior art dispensers. In one disclosed form, a closed negative pressure region is defined in part by a diaphragm molded from a single material. The diaphragm includes a relatively thick central disk, surrounded by a relatively thin flexure and peripheral ring. That construction is difficult to fabricate, in part due to the differing thickness regions.
According to one aspect of the present invention there is provided an improved dispensing device for use with a drug delivery system comprising a means for releasing a measured dose of medicament from the system, the releasing means comprising a means for applying a preload capable of actuating the delivery means in the system, a means for applying a resisting pneumatic force capable of preventing actuation of the delivery means and a release device capable of freeing the resisting pneumatic force to allow the preload to actuate the delivery means and dispense the medicament. The means for applying a resisting pneumatic force of the present invention is similar to that in U.S. Pat. No. 5,447,550 but includes a structure that is distinct from, and provides substantial improvement over, the corresponding structure in U.S. Pat. No. 5,447,150.
The pneumatic resisting means of the present invention is provided by air which is held at a negative pressure below atmospheric prior to release. That negative pressure provides a pneumatic resisting force which opposes the preload force. The release device acts to return the pressure to atmospheric or prior equilibrium, thus allowing the full force of the preload to act. The pneumatic resisting force is established by a negative pressure region defined in part by a diaphragm. The diaphragm includes a central disk of a first, relatively high stiffness material and a peripheral ring, coupled by a flexure of a second, relatively low stiffness material. In various forms, the peripheral ring may be of the same material as the flexure, or may be of a different material.
The device is particularly suited for use with pressurized inhalation aerosols having valves as the delivery means.
Although this device has been described in particular relation to a system using air, it will be realized that in a closed system any suitable gas could be used.
In a preferred arrangement, there is provided a breath actuated dispensing device for use with an aerosol medicant container for dispensing a medicant in a metered dose. The container is cylindrical and extends along a container axis between a first end and a second end. The container has a spring based aerosol valve at the first end, which is responsive to an axial force above a predetermined threshold to release the metered dose. The device includes a housing disposed about a central axis and having a first end and a second end, where the second end includes a shoulder and an expulsion nozzle extending therethrough. A support sleeve is disposed within the housing. The sleeve is adapted for axial motion along the central axis. The sleeve is further adapted to support the second end of the container, whereby the container axis is substantially coaxial with the central axis and the aerosol valve is positioned adjacent the shoulder and in communication with the expulsion nozzle. The device further includes a diaphragm assembly having a relatively rigid central disk, a peripheral attachment ring disposed about a peripheral portion of the disk, and an annular flexure extending between the peripheral portion of the disk and the attachment ring. The central disk is affixed to the first end of the housing and the peripheral ring is affixed to the sleeve, thereby defining a closed region between the diaphragm and the sleeve. A breath actuated valve assembly is provided to selectively establish in a first state an air flow path between the closed region and regions exterior thereto, and interrupting in a second state the air flow path. A spring force bias element is adapted to bias the sleeve toward the second end of the housing. When the breath actuated valve element is in the second state, pneumatic pressure in the closed region establishes a force on the sleeve opposite the bias. In that circumstance, the axial force on the aerosol valve is below the predetermined threshold, and whereby when the breath actuated valve element is in the first state, pneumatic pressure in the closed region establishes a substantially zero force on the sleeve and the bias is sufficient to drive the sleeve and the container toward the shoulder and establish an axial force on the aerosol valve above the predetermined threshold.
Preferably, the central disk is made of a first material characterized by a relatively high stiffness, and the annular flexure is made of a second material characterized by a relatively low stiffness. The annular flexure is bonded to the disk, whereby the disk, the annular flexure and the peripheral ring form a contiguous assembly. In an alternative form, the ring and flexure may be different material as well. Preferably, the multimaterial diaphragm is made using a multishot molding process wherein a first portion (such as the disk) is molded in a first step, and a second portion (such as the flexure and ring) molded in a second step, and at the same time bonded to the first portion.
It is also preferred that the release device is breath-actuated in order to co-ordinate the release of the medicament with the intake of breath. The favored breath-actuating means comprises a moveable vane mechanism. This vane mechanism may be housed in the upper part of the chamber. A valve seal is preferably attached to said vane, such that on inhalation the vane moves from its rest position to its actuating position, thus moving the valve seal out of contact with the valve port, causing the opening of the valve. The vane mechanism is preferably biased towards its closed position, e.g., by a spring. When the valve opens, an air flow path is established between the negative pressure region and regions exterior thereto.
The outer chamber may include air inlets allowing passage of air to the mouthpiece of the device. The inlets may take the form of slots or of an air porous membrane. The latter is particularly suitable to help filter dust.
The medicament may be a drug per se or on any form of carrier, e.g. including a powder or a gaseous carrier.